216 THE TRUE FUNGI 



plant, the sexual generation, characterized by the reduced 

 number of chromosomes and the production of the sexual organs, 

 and the asexual generation, characterized by the double number 

 of chromosomes \vhich appear in two spore-bearing plants, i. e., 

 the minute plant in the cystocarp and the tetraspore-bearing 

 plant. The distinction between the sexual and asexual genera- 

 tion is emphasized at this point because we see in the algae how 

 it gradually became more and more conspicuous, and in the 

 mosses and succeeding groups it will be noticed that the relation 

 of these two generations is intimately associated with the evolu- 

 tion of the higher types of plant life. 



Subdivision 5. Eumycetes or True Fungi 



76. The Nature of Fungi. The Fungi are the largest group 

 of the Thallophyta and include such familiar forms as moulds, 

 mildews, toadstools and mushrooms. The absence of chloro- 

 phyll is the most striking feature of these plants. They are 

 unable therefore to form sugar, starch and other foods from the 

 elements of the soil and air and must obtain them already manu- 

 factured. Consequently, they are either saprophytes living upon 

 decaying organic matter, or parasites preying upon living organ- 

 isms. It is quite possible that this mode of life is responsible 

 for the disappearance of the chlorophyll. You have seen that 

 the accumulation of sugar in the chlorophyll bearing cells stops 

 their activity. So here the absorption of organic material from 

 plants and animals may have had the same result and so led to 

 the disappearance of chlorophyll. The majority of fungi procure 

 their food from decaying plant and animal matter, and in this 

 relation many of them arc of the same economic importance as 

 the saprophytic bacteria. Other forms exist as parasites upon 

 living plants and animals. In this relation fungi cause almost 

 incalculable loss annually to the country and frequently crops 

 over large areas are ruined by their depredations. The parasitic 

 forms gain access to the host through a wound, stoma or the 

 delicate tissues of seedlings or young parts of the plant, and in 

 other cases the fungus forms a ferment that dissolves the cell 

 walls and thus opens the w*ay for the entrance of the pest. The 



